The Jewish Leadership Council and the Board of Deputies of British Jews protest in Parliament Square against antisemitism in the Labour party.
Photograph: Wiktor Szymanowicz/Rex/Shutterstock

Momentum has warned its supporters that accusations of antisemitism in Labour are not rightwing smears or conspiracy, saying unconscious anti-Jewish bias is “more widespread in the Labour party than many of us had understood even a few months ago”.

The group accused the party of failing to deal satisfactorily with the problem and said it had begun a process with external groups of developing antisemitism awareness training for Labour members.

The highest governing body of the grassroots group, a key force behind Jeremy Corbyn, agreed the statement over the weekend by email, the Guardian understands. It says political opponents of the Labour leader have been using the problem opportunistically, but that should not be an excuse not to tackle it.

The statement was agreed by the 26 members of Momentum’s national coordinating group, which includes Christine Shawcroft, the former chair of Labour’s disputes panel, who resigned from that role and her place on the party’s national executive committee (NEC) after it emerged she had defended a council candidate accused of Holocaust denial.

New elections are taking place for Momentum’s NCG, which also includes the Momentum founder, Jon Lansman, with ballots sent out on Monday. It is understood Shawcroft has decided not to run for re-election but remains a director of Momentum.

Momentum said it “acknowledges the anger, upset and despair within the British Jewish community at the numerous cases of antisemitism in the Labour party” and said it was disappointed in the party’s “failure to date to deal with them in a sufficiently decisive, swift and transparent manner”.

The statement said: “Accusations of antisemitism should not and cannot be dismissed simply as rightwing smears nor as the result of conspiracies.

“Current examples of antisemitism within the Labour party are not only a problem of a few, extreme ‘bad apples’, but also of unconscious bias, which manifests itself in varied, nuanced and subtle ways and is more widespread in the Labour party than many of us had understood even a few months ago.”

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However, Momentum’s national coordinating group said it was possible both to accept that antisemitism was a problem on parts of the left while also accepting that Corbyn had been attacked “using this issue as a way to undermine his leadership”.

“The actions of others do not reduce our responsibility to challenge antisemitism whenever and wherever it occurs,” the statement added.

Shawcroft had previously used a Facebook post to insist the issue was “being stirred up to attack Jeremy”, before resigning from the NEC.

Jennie Formby with Iain McNicol, after she was appointed as the party’s new general secretary. She said: ‘This sort of abuse has no place in the Labour party.’ Photograph: Stefan Rousseau/PA

Meanwhile a letter to the Guardian signed by more than 40 senior academics called for an end to “Corbyn’s trial by media” over antisemitism.

Momentum’s coordinating group statement said the anger about antisemitism reinforced the need for a new programme of political education in Labour, which could examine unconscious bias that would “move people away from conspiratorial thinking and towards a systematic understanding of how society and capitalism works”.

The group said it was also reviewing its own constitution and complaints procedures as a “practical commitment to stamping out antisemitism and all forms of discrimination”, and disseminating further guidance to local groups.

Lansman, a veteran leftwinger who stood but then withdrew as a candidate to replace Iain McNicol as Labour’s general secretary, was himself the subject of antisemitic attacks after he decided to stand against Unite’s Jennie Formby for the role last month.

During the process, Formby said the attacks were “disgraceful and must stop … this sort of abuse has no place in the Labour party”.

Another key Corbyn ally, Rhea Wolfson, a Jewish Momentum activist who is also a member of Labour’s NEC, said on Monday she had also been frustrated with the slow pace of tackling antisemitism complaints.

Wolfson said Formby, who was appointed to succeed McNicol, would make the issue a top priority.

“There is very clearly a real issue, a huge piece of work that needs to be done in the Labour party, around modern antisemitism and giving people the tools to recognise when legitimate criticism of Israel crosses the line into antisemitism,” she told BBC Radio 4’s Today programme.

Momentum’s statement was greeted with caution from some groups. The Jewish Labour Movement’s Ivor Caplin said Momentum had been “part of the problem” by allowing expelled or suspended activists to organise in local movements and said it had “belatedly woken up to the challenges.”

“We now need action not words across the wider Labour movement and that includes Momentum whose leaders sit around Labour’s top table,” he said.

Richard Angell, director of Labour’s centrist pressure group Progress, said the group needed to tackle any abuse from supporters on Momentum Facebook or Twitter pages. “They need send a clear message to individuals with Momentum symbols in their social media profiles to ‘delete their tweet or delete their twibbon – you do not speak for us’,” he said.

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It emerged on Monday that another Labour local election candidate had been suspended after apparently sharing Facebook posts urging people to question the Holocaust.

Roy Smart, a candidate in Tunbridge Wells, appeared to share links to a site in 2015 calling itself a “Holocaust Deprogramming Course”. Another post from September 2017 said: “People being allowed to question if the Holocaust happened is not the same as being a Holocaust denier.”

Labour has suspended Smart pending an investigation and will choose a new candidate for the council seat. A party spokesperson said: “Labour takes all complaints of antisemitism extremely seriously, [these are] fully investigated and appropriate disciplinary action taken in line with our rules and procedures.”